pressure 3

[nicolasdegand]

Hi,

If I apply an uniform pressure of 45 bars for example to a circular plate and I extract the results, I don't understand why the pressure I extract (until 172!) in the centre node of the plate is bigger than the pressure I applied????

thanks a lot,

nico

 

[bassmanjax]

Hi Nico

Could you please explain which result value you are extracting?

Martin

 

[nicolasdegand]

Hi Martin,

I just extract the evolution of the time-pressure in the node situated in the centre of the plate:ODP field output>unique nodal>stress component>Sressure PI: part-1-1 N:1

 

[corus]

The stress component acting in the direction away from the plate surface should equal the applied pressure, approximately. The values can be plotted as contours, and will be contant at every point on the surface for this stress component .

corus

 

[bassmanjax]

Hi Nico

You'll have to look in the documentation to verify this, but I believe that the result value is the pressure stress at that node - it is an (extrapolated) measure of the stress in the parent elemnent due to volumetric change.

Martin

 

[xerf]

The stress field is computed at integration points. In order to obtain the "unique nodal" values, the values at the integration points are extrapolated at the nodes. Since a node is shared by several elements, each element can provide an extrapolated stress (component) value at the shared node. Further, an additional averaging algorithm it is used and
the "unique" nodal value is obtained. This type of values is used for banded contour plot. (The quilt countout plot does not use this approach). This algorithm can be tuned using CAE/Visualization->Results->Options.

Thus, if you have strong gradients within the elements sharing the same node, or even among the integration points of the same element it is possible to get strange "unique" nodal values. For example, you can get negative values for the quantities that cannot have a negative value, e.g. PEEQ (equivalent plastic strain).